Radio Frequency (RF) and optical communications systems are subject to a variety of conditions that can degrade performance, including environmental conditions, discrepancies in design, and conditions inherent in the physical characteristics of system components. These conditions may include noise/interference from various sources (electrical or optical), intermodulation, and similar anomalies. Any real (i.e., non-ideal) amplifier will add noise to whatever signal it is amplifying, which noise may be quantified by the amplifier noise figure. Any nonlinear system may also impart intermodulation among different frequencies (channels) operating within the system. These effects become more pronounced as component characteristics change with time and/or temperature.